82 



CARBONIFEROUS ENTOMOSTRACA. 



CARBONIFEROUS ENTOMIDIDiE. 



EntomidiDvE, Jones, 1870. Month. Microsc. Journ., vol. iv, p. 187. 



— — 1873. Ann. Mag. Nat. Hist., ser. 4, vol. xi, p. 417. 



Under the heading Entomidid^e two genera, Entomis and Entomidella, have been 

 grouped on account of their extremely developed nuchal furrow, thus standing apart 

 from the other known Ostracoda, recent and fossil. They differ from those Cypridinads 

 which have a nuchal furrow by the absence of a frontal notch. 



In 1870^ Entomis and Entomidella were included with the Cypridinad<2, but in 

 1873 ^ they were separated off as a distinct group — Entomididce — on account of the 

 intensity of their dorsal sulcus, the absence of frontal sinus and hook, and their more or 

 less concentric ornament. It was the apparent similarity of the transverse ridging in 

 Entomis Koninckiana and E. Burrovii (Plate IV, figs. 20 and 21) to that in some 

 CyprelltjB, shown in the same plate, that led to the collocation of these forms on that 

 Plate. The real difference, however, in the ridging (that of Cyprella being discon- 

 tinuous, whereas that of Entomis is continued by curvatures on the ventral region) was 

 soon recognised, and these Entomididce have had to remain undescribed until the 

 Platycopa were treated of in their right place. 



The EntomididdB are more closely related to some members of the Leper ditiadce" than 

 to any other known genera. Their deep dorsal or nuchal furrow is an exaggeration of 

 that in Primitia, BeyricJiia, and Kirhbya. Indeed, there is a faint trace of it in 

 Leperditia and Isochilina. The plan of concentric ridging is present also in some 

 Kirkbyce. Hence we think that provisionally we may place the Entomididce close to the 

 Lejjerditiadce . As some good Carboniferous species have been figured in Plate IV we 

 proceed to describe them. 



ENTOMIS, Jones, 1861. 



1841 and 1844 Cypridina (in part), De Koninck, Nouv. Mem. Acad. Roy. Sci. et 



Belles Lettres de Bruxelles, vol. xiv, 1841, Mem. 

 Crust, foss. Belg., p. 18; Descript. Anim. foss. Carb. 

 Belg., 1844, p. 587. 



1 ' Monthly Microsc. Journ.,' vol. iv, 1870, p. 187. 



2 Ibid,, vol. X, 1873, p. 77. 

 ^ Ibid., vol. iv, p. 187. 



